Subscribers receive multiple services, such as voice, video, and data, from a single provider. Often, the services are combined for delivery over a single physical layer, such as twisted pair, coaxial cable, or fiber. As voice and video service has traditionally been provided through a dedicated connection, subscribers expect reliable service and can be intolerant of even minor disruptions such as dropped calls or loss of picture. However, as services such as voice-over-IP (VoIP) or Internet Television (IPTV) are combined with data service, a single point of failure is introduced for the combined services and heavy use of the data service can impact the quality of the voice and video services.
The use of the same reference symbols in different drawings indicates similar or identical items.